Variations in Some Morphological and Pigmental Characteristics in Rhododendron kaempferi Planch., R. kiusianum Makino and Their Natural Hybrids on Kirishima Mountain Mass.

Abstract

Rhododendron kaempferi Planch., at the foot of the Kirishima mountain mass, exhibited narrow range of variations in flower colour and petal blotch expression, producing vermilion shaded flowers with prominent blotches, except for the flower size showing a wide range of variation. Petal chemical pigmentation also showed a narrow range of variation. Anthocyanin of the cyanidin series was only observed. In addition, at the summit of the mountain mass, R. kiusianum Makino occurred with narrow range of variations, producing small, exclusively purple and almost blotchless flowers. Variations in chemical pigmentation were rarely observed. Anthocyanins of the delphinidin series and 5-methylated flavonols occurred in all individuals.On the other hand, azaleas on the slopes of the mountain mass showed wide phenotypic characteristics. The flower colour ranged from vermilion through pink to purple, the flower size ranged in diameter from 16 to 60 mm and the petal blotch expression was diverse. As regards chemical pigmentation, a wide range of variation was apparent. Moreover, phenotypic and pigmental characteristics of these azaleas varied according to the altitude of their habitats. The lower the altitude, the more the azaleas became similar to R. kaempferi, while the higher the altitude, the azaleas came to resemble R. kiusianum more closely.In view of the extremely wide phenotypic and pigmental characteristics, and the changes in the characteristics from those of R. kaempferi through the intermediate forms to those of R. kiusianum as altitude increased, azaleas on the slopes of the mountain seemed to be the result of natural hybridization between R. kaempferi and R. kiusianum.